It is well known that water-based coolants are commonly used to cool machine tools during cutting or other operations of the tools. Typically, the coolant solutions are applied to heated components of the tool, and either recirculated through machine or collected for subsequent usage. Such used water-based coolants frequently contain contaminants such as lubricating oils from the machine tools, and metal particles. These coolants may be recirculated and cleaned in a continuous operation, or they may be removed for storage and reprocessing. When the coolants are recirculated, oil and debris collect to form an immiscible film on surfaces of the coolant. Such a film, when not removed, facilitates aerobic degradation of the coolant, and hence shortens coolant life and inhibits optimal performance of the machine tool. Therefore, it is desirable to recycle such coolants for many reasons, including enhanced performance, as well as the high cost of purchase and/or disposal of the coolants, etc. Typically the used coolants are stored in barrels or similar containers wherein the coolants separate from non-soluble, immiscible oil or other liquid contaminants so that the oil forms a liquid layer floating on top of the water-based coolant.
It is known to use different kinds of separating devices to process such layered fluids of coolant and oil in order to remove the oil and other contaminants from the coolant. Thereafter the water-based coolants can also be processed for subsequent usage, such as disclosed in U.S. Pat. No. 5,026,488 to Mescheau that issued on Jun. 25, 1991 for a “Liquid Recycling System”. A less complicated and more typical separating apparatus is disclosed in U.S. Pat. No. 4,274,957 to Koller that issued on Jun. 23, 1981. Those patents are hereby incorporated herein by reference. Koller shows a portable, self-contained skimmer that uses an endless, flexible belt that is extended through an opening in a top of a barrel of collected, contaminated coolant. Contaminating oil is attached and/or adsorbed by the belt and passes with the belt into a housing having a drive motor for moving the endless belt. The housing also has a drive roller and a pinch or deflection roller that cooperate to squeeze the attached and/or adsorbed oil and any amount of accompanying coolant off the belt, and the oil and any coolant then pass along a trough in the housing and out of a spout into a container for holding the separated oil. The belt moves continuously through the layer of oil until the oil is removed. The water-based coolant may then be further processed if necessary for recycling usage.
Known separators of such immiscible liquids provide for some effective separation, but they also have major difficulties. For example, such self-contained skimmer separators as shown in Koller do not have controllers to cycle operation times for automated, efficient operation. Simply running such skimmers indefinitely tends to increase an amount of water-based coolant separated with the oil as the oil layer decreases in thickness. Also, known skimmer separators simply provide for storage of the separated oil in a container with no control system for avoiding overflow of the container. Overflow of separated lubricants onto a factory floor presents very substantial risks for accidents resulting from such spillage. Avoiding such overflows would require a considerable expenditure of manual labor to start, monitor and stop such skimmer separators. Additionally, it is known that separated lubricants include dissolved gases and suspended metal contaminants, so pumping separated contaminating oils presents substantial challenges for any pumping and collecting system. The suspended metal particles will rapidly degrade most impeller types of pumps, and movement and storage of the separated oil contaminants give rise to foaming and consequent transport and storage problems.
It is also known that separating oil from water is an enormous environmental concern related to accidental contamination of various waterways within our environment. Systems utilized for separating oil contaminants from machine tool coolants may also be utilized for separating, transporting and collecting contaminating oils from environmental oil spillages, for example in oceans, lakes, ponds, and streams, etc. Any such oil separating systems, however, will necessarily suffer from the structural limitations facing known separators of oil contaminants of water-based coolants. Consequently, there is a need for an improved system for separating mixed immiscible liquids that is durable, automatic, inexpensive to manufacture and operate, and that minimizes risks of spillage of separated liquids.